Cyclone separators are well-known devices for separating solids from gases and gases from liquids. Some typical cyclone separator designs are illustrated in Perry's Chemical Engineers' Handbook, published by McGraw-Hill Book Company, New York City. In conventional cyclones, spin is imparted to the vapor and entrained liquid after it enters the cyclone via a downcomer or plenum. The vapor and entrained liquid then moves upward,entering a zone where liquid is removed via slots or other perforations in the barrel or by an annular hat in the top of the barrel.
The use of vanes within cyclones is well-known. They are used to guide the flow of gases and minimize entrainment of liquids or solids. U.S. Pat. No. 3,969,096 (Richard) discloses a cyclone separator having multiple vaned gas inlets. The gas inlet consists of elongated inlet openings (like those of a louver) positioned to deflect incoming gas in a circular path from the gas outlet tube.
Some means of preventing backflow from cyclonic devices are known. U.S. Pat. No. 4,701,307 (Walters et al.) discloses a ballistic separation device that results from surrounding the downstream end of a progressive flow reactor or riser reactor with a concentric conduit that is in fluid communication with a cyclone separator. The device may also include a bevelled lip or projection at the axial opening of the progressive flow reactor. In Walters, vapor is being separated from solid, as opposed to vapor being separated from liquid as in the instant invention.
Shrouds on the inlet of a cyclone, rather than on the outlet, are illustrated in U.S. Pat. No. 5,266,187.